Lots of teams charge more when premium teams are in town. This is just the most convoluted plot I've seen. (Granted, I don't see a lot of plots.)
I suppose, technically, it hurts the folks coming down from Chicago because they're less likely to want to see one of the other games, but if you can afford to travel from Chicago, stay in Nashville, and go to the game, you can probably afford to buy the ticket to the extra game and sell it later. The catch is that you have to find someone to sell it to that actually wants to watch the Preds play.
That might be difficult in person, but with modern technology, it shouldn't be that bad. Savvy Hawks fans will realize that buying their extra ticket to a game played with a nearby opponent (St. Louis comes to mind) would make the re-sell easier. Savvy St. Louis fans are probably planning to buy their tickets on StubHub.
At the end of the day, it's another gimmick that has gotten the Preds some free publicity.
No news yet as to whether or not Blackhawks fans will be required to buy some of that melted Golden Ice.